Fixes CVE-2019-5435. It looks like this is not a problem on 32-bit
Windows because fortunately we don't use /LARGEADDRESSAWARE flag
to set IMAGE_FILE_LARGE_ADDRESS_AWARE... but on 32-bit Linux
the user-space VM is 3GB so an exploit might be possible.

Apparently there's no code in LO that uses the CURLU_URLENCODE flag.

The other one, CVE-2019-5436, doesn't matter because we disable tftp.

Change-Id: I0d4f087befa5a3c4fb21ec36761dad68932425d9
Reviewed-on: https://gerrit.libreoffice.org/72732
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>